1. Field of the Invention
The present invention relates to light-emitting devices, such as organic light emitting diodes (LEDs), and power-generating devices.
2. Description of the Related Art
Light-emitting devices such as organic LEDs have been widely used for purposes such as displays, backlights and illumination.
A light-emitting device in general includes, on a substrate, a first electrode, a second electrode, and a light-emitting layer disposed between the electrodes. When electric voltage is applied to the electrodes, holes and electrons are injected from each of the electrodes into the light-emitting layer. Recombination of the holes and electrons inside the light-emitting layer generates binding energy, which excites light-emitting material inside the light-emitting layer. When the excited light-emitting material returns to the ground state, light emission occurs, and the light may be extracted outside, taking advantage of the light emission.
In recent years, a light-emitting device provided with various types of light-extraction structures has been proposed, in order to enhance light-extraction efficiency of the light-emitting device.
For example, according to International Publication No. WO/2009/017035, light-extraction efficiency of a light-emitting device is enhanced by providing, between a glass substrate and a clear electrode, a scattering layer with high refractive index. Furthermore, according to Japanese Translation of OCT International Application Publication No. JP-T-2012-512518, Japanese Unexamined Patent Application Publication No. 2009-9861, and Japanese Unexamined Patent Application Publication No. 2004-182490, light-extraction efficiency of a light-emitting device is enhanced by providing a diffracting structure, a corrugated structure, and a layer with a low refractive index, as a light-extraction structure, respectively.